This invention relates to a substrate processing system and/or a substrate conveying method, usable in a semiconductor device or liquid crystal display panel manufacturing process, for example, to convey a substrate to be processed (such as a semiconductor wafer or a liquid crystal display substrate, for example) to a process chamber to process the same therein.
In exposure apparatuses for transferring in very fine pattern such as a circuit pattern onto a substrate such as a semiconductor wafer or a liquid crystal display substrate, further reduction in linewidth of a transferred pattern as well as further increase of throughput have been desired. The narrowing of the linewidth of a transferred pattern requires shortening of the wavelength of exposure light to be used for exposure (photoprinting), and the wavelength shortening is made by using g-line, i-line and then a KrF laser, for example. Among these light sources, X-rays to be emitted from a synchrotron ring are considered to be a short wavelength light source suitable for transferring a very fine pattern. Here, since such X-rays are much attenuated in atmosphere, usually, an exposure unit of an exposure apparatus is accommodated in a chamber while the chamber inside space is filled with a reduced pressure of He ambience, less attenuating X-rays, and the exposure process is performed therein.
In such exposure apparatuses, a substrate to be processed such as a Si wafer, for example, should be conveyed between an exposure process unit inside a chamber and a substrate supply unit in an atmosphere. To this end, a load-lock chamber is provided between them, such that each substrate is conveyed through the load-lock chamber.
FIG. 3 shows a general structure of a known type wafer processing system with a load-lock chamber wherein one or more wafers can be accommodated.
As shown in FIG. 3, this type of wafer processing system comprises a chamber 102 for accommodating therein a process station where a process such as an exposure process to a wafer, for example, is to be performed in an ambience different from the atmosphere, as well as a load-lock chamber 103 and a wafer supply station 110 which is disposed in the atmosphere. The load-lock chamber 103 is provided with an atmosphere side gate valve 105 for isolating the load-lock chamber 103 from the wafer supply station 110 in the atmosphere, and a chamber side gate valve 106 for isolating the load-lock chamber 103 from the chamber 102. Further, the load-lock chamber 103 is provided with a gas discharging means (not shown) for discharging a gas out of the chamber, and gas supply means (not shown) for supplying a gas of He or N2 into the chamber. Also, there is a table (not shown) on which a wafer is to be placed. Inside the chamber 102, there is conveying means 107 for conveying a wafer between the load-lock chamber 103 and the process station. Also, there is conveying means 108 for conveying a wafer between the wafer supply station 110 in the atmosphere and the load-lock chamber 103.
In operation of the load-lock chamber 103, when the atmosphere side gate valve 105 is kept opened and one or more wafers are supplied into the chamber from a wafer carrier 104 which is placed at the wafer supply station 110 in the atmosphere, the atmosphere side gate valve 105 is closed and then ambience replacement is carried out by using the gas discharging means and the gas supplying means. Thereafter, as an ambience the same as the inside ambience of the chamber 102 is established inside the load-lock chamber 103, the chamber side gate valve 106 is opened, such that, by the conveying means 107 inside the chamber 102, a wafer or wafers inside the load-lock chamber 103 are taken out and conveyed to the process station. After a predetermined process is made to the wafer at the process station, the wafer is moved back to the load-lock chamber 103 by the conveying means 107. Then, through the load-lock chamber 103, the wafer is conveyed back to the water carrier 104. Thereafter, through repetition of similar operations, conveyances and processes of wafers are made sequentially.
As regards the conveyance sequence of this wafer processing system, the wafer supply to the process station where an exposure process or the like is made and the wafer collection from the process station are made in parallel to each other. More specifically, there is a temporary wafer storage space before the process station. After a process is completed, a processed wafer at the process station is temporarily collected to the temporary storage space. Then, promptly after a wafer to be processed next is conveyed to the process station, the processed wafer at the temporary storage space is conveyed to the load-lock chamber. The processed wafer inside the load-lock chamber is moved out of the chamber and is collected to the wafer carrier at the wafer supply station in the atmosphere. Promptly after it, a subsequent wafer is conveyed into the load-lock chamber, and the ambience replacement is carried out.
FIG. 4 shows another type of wafer processing system having a sending-in load-lock chamber and a sending-out load-lock chamber separately. In FIG. 4, the wafer processing unit comprises a chamber 202 for accommodating therein a process station for processing a wafer in an ambience different from the atmosphere, a sending-in load-lock chamber 203, a sending-out load-lock chamber 203a, and a wafer supply station 210 which is disposed in the atmosphere. The load-lock chambers 203 and 203a are provided with atmosphere side gate valves 205 and 205a for isolating the load-lock chambers from the wafer supply station 210 in the atmosphere, as well as chamber side gate valves 206 and 206a for isolating them from the chamber 202. Further, the load-lock chambers 203 and 203a are provided with gas discharging means (not shown) for discharging a gas from the load-lock chambers, and gas supplying means (not shown) for supplying a gas of He or N2 into these chambers. Furthermore, the load-lock chambers 203 and 203a are provided with a table (not shown) on which a wafer carrier for accommodating plural wafers (e.g., 25 wafers) therein is to be placed. Inside the chamber 202, there is conveying means 207 for conveying wafers between the process station and the load-lock chambers 203 and 203a. Another conveying means 208 is provided to convey a wafer carrier 24 between the wafer supply station 210 in the atmosphere and the load-lock chambers 203 and 203a. 
In such a wafer processing system, a wafer carrier 204 having plural wafers accommodated therein is conveyed from the wafer supply station 210 into the sending-in load-lock chamber 203 by use of the conveying means 208 or by an operator, and then it is placed on the table inside the load-lock chamber 203. At this moment, the atmosphere side gate valve 205 of the load-lock chamber 203 is open to the atmosphere. After the wafer carrier 204 is conveyed into the load-lock chamber 203, the gate valve 205 is closed and replacement of the inside ambience of the load-lock chamber 203 is carried out. As an ambience the same as the inside ambience of the chamber 202 is established inside the load-lock chamber 203, the chamber side gate valve 206 is opened, such that, by the conveying means 207 inside the chamber 202, a wafer or wafers inside the load-lock chamber 203 are taken out and conveyed to the process station inside the chamber 202. After a predetermined process is made to the wafer at the process station, the wafer is conveyed to the sending-out load-lock chamber 203a by the conveying means 207. Here, the wafer carrier 204 has been set in the sending-out load-lock chamber 203a, and also an ambience the same as the inside ambience of the chamber 202 has been set inside the load-lock chamber 203a. After wafers of a predetermined number are processed and they are accommodated into the wafer carrier 204 inside the load-lock chamber 203a, the chamber side gate valve 206a is closed. Then, replacement of the inside ambience of the load-lock chamber 203a is carried out and, after it, the atmosphere side gate valve 205a is opened. Thereafter, the wafer carrier 204 is conveyed to the wafer supply station 210 by use of the conveying means 208 or by the separator.
A wafer processing system of a further example comprises plural load-lock chambers, and a wafer carrier placement station is provided in an atmosphere. Conveying means which is accessible to the wafer carrier placement station and the load-lock chambers is disposed in the atmosphere. By using this conveying means, wafers are taken out of a wafer carrier at the wafer carrier placement station, and they are conveyed to the load-lock chambers.
In exposure apparatuses, as described hereinbefore, a further reduction in printed linewidth as well as a further improvement of throughput are required. As regards the requirement of higher throughput, in X-ray exposure apparatuses, the exposure process time can be shortened well. However, in substrate supplying and conveying systems for supplying and conveying substrates such as wafers. The time for replacement of an ambience gas in a load-lock chamber raises a problem. More specifically, in the load-lock chamber, it is necessary to perform an operation for replacement of an atmosphere and a reduced pressure He ambience gas should be done. There is a limit to shortening the time for the ambience replacement.
Further, in order to improve the throughput, the wafer conveyance time and the load-lock chamber ambience replacement time should be made shorter than the wafer process time. However, where bi-directional conveyance (i.e., sending a wafer into and out of a reduced pressure He ambience) is considered, the wafer conveyance time including the load-lock chamber ambience replacement is a bar to the improvement of the throughput.
Namely, the total time corresponding to the sum of (i) the time necessary for the load-lock chamber ambience replacement from the atmosphere to a reduced pressure He ambience and then from the reduced pressure He ambience to the atmosphere and (ii) the time necessary for the wafer conveyance, must be shorter than the wafer exposure process time. If the load-lock chamber ambience replacement time cannot be shortened physically, the throughput cannot be improved. Even in a case wherein the wafer conveyance is quick, if the load-lock chamber ambience replacement time is longer, a wafer must be stopped before the load-lock chamber until the ambience replacement is completed. This is very inefficient with respect to the throughput.
For example, the wafer conveyance sequence through the load-lock chamber in the wafer processing system shown in FIG. 3 may be done in the manner as illustrated in FIG. 5.
In FIG. 5. denoted at 101 is the exposure station inside the chamber 102, and denoted at 103 is the load-lock chamber. Denoted at 104 is the wafer carrier disposed at the supply station in the atmosphere. Denoted at 107 and 108 are conveying means inside the chamber and conveying means in the atmosphere, respectively. Denoted at 109 is a standby station where a water to which an exposure process is completed is temporarily held. Arrows in the drawing depict the state of wafer conveyance or wafer transfer. Mesh portions each illustrates the place where a wafer is present. When a wafer is present inside the load-lock chamber 103, it means that the ambience replacement from a reduced pressure He gas to the atmosphere or from the atmosphere to the reduced pressure He ambience has been accomplished inside the load-lock chamber.
At step S101, a wafer stored in the wafer carrier 104 is taken out of the carrier by the conveying means 108, and it is conveyed toward the load-lock chamber 103. At this moment, the load-lock chamber 103 is open to the atmosphere. At step S102, the wafer is moved into the load-lock chamber 103, and the ambience replacement from the atmosphere to the reduced pressure He gas is carried out therein. At step S103, the wafer inside the load-lock chamber 103 is conveyed onto the exposure station 101 by the conveying means 107. At step S104, an exposure process to the wafer is carried out at the exposure station 101. At this time, in the load-lock chamber 103, the ambience replacement from the reduced pressure He gas to the atmosphere is carried out.
Subsequently, at step S510, the wafer having been exposed at the exposure station 101 is transferred from the exposure station 101 to the stand-by station 109. Simultaneously therewith, a second wafer to be processed next is taken out of the wafer carrier 104 by the conveying means 108, and it is conveyed to the load-lock chamber 103. At step S106, the wafer to which the exposure process has been completed is present at the stand-by station, while the second wafer is present in the load-lock chamber 103. In the load-lock chamber 103, ambience replacement from the atmosphere to a reduced pressure He gas is carried out. At step S107, the second wafer inside the load-lock chamber 103 is conveyed to the exposure station 101 by the conveying means 107. At step S108, an exposure process to the second wafer is carried out at the exposure station 101. Simultaneously therewith, the already exposed wafer which is present at the stand-by station 109 is collected into the load-lock ch mber 103 by the conveying means 107.
Subsequently, at step S109, the wafer having been exposed at the exposure station 101 is transferred to the stand-by station. There is a wafer in the load-lock chamber 103, and the ambience replacement from the reduced pressure He gas to the atmosphere is carried out in the load-lock chamber 103. Thereafter, at step S110, while the exposed wafer is kept at the stand-by station 109, the wafer inside the load-lock chamber 103 is collected into the wafer carrier 104 by the conveying means 108. Subsequently, at step S111, a third wafer stored in the wafer carrier 104 is taken Out by the conveying means 108, and it is conveyed to the load-lock chamber 103. At step S112, in the load-lock chamber 103 wherein the third wafer is present, the ambience replacement from the atmosphere to a reduced pressure He gas is carried out. During this time period, the already exposed wafer is held at the stand-by station 109.
Thereafter, similarly to step S107, the third wafer in the load-lock chamber 103 is conveyed to the exposure station 101 by the conveying means 107 and. at step S108, an exposure process is performed to the third wafer at the exposure station 101. Simultaneously therewith, the already exposed wafer held at the stand-by position 109 is collected into the load-lock chamber 103 by the conveying mean:s 107. After this, the operations at steps S107-S112 are repeated to perform exposure processes to wafers of a predetermined number.
In the wafer conveyance sequence in such a wafer processing system, the total time of the wafer conveyance time plus the time for ambience replacement of the load-lock chamber is longer than the time necessary for the exposure process. As a result, like at steps S110-S112, there is a useless time in which no exposure process is performed at the exposure station.
This state can be expressed by equations, as follows. Now, the time for ambience replacement in the load-lock chamber from the reduced pressure He ambience to atmosphere is denoted by Thxe2x86x92a, the time for replacement form the atmosphere to reduced pressure He ambience is denoted by Taxe2x86x92h, the wafer conveyance time is denoted by Ttr, and the wafer process time at the exposure station, including the exposure time, is denoted by Tex. Here, if the relation
Texxe2x89xa7Thxe2x86x92a+Taxe2x86x92h+Ttr
is not satisfied, the wafer conveyance time or the load-lock chamber ambience replacement time raises a problem with respect to enlargement of the throughput.
Further, in the wafer processing system such as shown in FIG. 4 wherein there are separate sending-in and sending-out load-lock chambers, while the wafer conveyance into and from the reduced pressure He ambience is taken into account, a relation
Tex/2xe2x89xa7Thxe2x86x92a+Taxe2x86x92h+Ttr
should be satisfied. Thus, the requirement to the wafer conveyance time and the load-lock chamber ambience replacement time is very strict.
In the wafer processing system of FIG. 4, the wafer conveyance sequence with plural load-lock chambers may be done such as shown in FIG. 6.
In FIG. 6, denoted at 201 is the exposure station inside the chamber 202, and denoted at 203 is the sending-in load-lock chamber. Denoted at 204 is the wafer carrier disposed at the supply station in the atmosphere. Denoted at 207 and 208 are conveying means inside the chamber and conveying means in the atmosphere, respectively. Denoted at 209 is a stand-by station where a wafer to which an exposure process is completed is temporarily held. Arrows in the drawing depict the state of wafer conveyance or wafer transfer. Mesh portions each illustrates the place where a wafer is present. When a wafer is present inside the load-lock chamber 203 or 203a, it means that the ambience replacement from a reduced pressure He gas to the atmosphere or from the atmosphere to the reduced pressure He ambience has been accomplished inside that load-lock chamber.
At step S201, a wafer stored in the wafer carrier 204 is taken out of the carrier by the conveying means 208, and it is conveyed toward the sending-in load-lock chamber 203. At this moment, the load-lock chamber 203 is open to the atmosphere. At step S202, in the load-lock chamber 103 having a wafer conveyed therein, the ambience replacement from the atmosphere to the reduced pressure He gas is carried out. At step S203, the wafer inside the load-lock chamber 203 is conveyed to the exposure station 201 by the conveying means 207. At step S204, an exposure process to the wafer is carried out at the exposure station 201. At this time, in the load-lock chamber 203, the ambience replacement from the reduced pressure He gas to the atmosphere is carried out.
Subsequently, at step S205, the wafer having been exposed at the exposure station 201 is transferred from the exposure station 201 to the stand-by station 209. Simultaneously therewith, a second wafer to be processed next is taken out of the wafer carrier 204 by the conveying means 208, and it is conveyed to the sending-in load-lock chamber 203 having been replaced by an atmosphere ambience. At this moment, in the sending-out load-lock chamber 203a, the ambience replacement from the atmosphere to a reduced pressure He gas is carried out. At step S206, the wafer at the stand-by station 209 to which the exposure process has been completed is conveyed by the conveying means 207 to the load-lock chamber 203a having a reduced pressure He ambience. At the same time, in the load-lock chamber 203, ambience replacement from the reduced pressure He ambience to the atmosphere is carried out. Then, at step S207, the second wafer inside the sending-in load-lock chamber 203 is conveyed to the exposure station 201 by load-lock chamber 203a, the ambience replacement from the reduced pressure He to the atmosphere is carried out. At step S208, an exposure process to the second wafer is carried out at the exposure station 201. Simultaneously therewith, the already exposed wafer is conveyed by the conveying means 208 from the sending-out load-lock chamber 203a to the wafer carrier 204. Also, in the sending-in load-lock chamber 203, ambience replacement from the reduced pressure He gas to the atmosphere is carried out. Subsequently, like step S205, the wafer having been exposed at the exposure station 201 is transferred to the stand-by station 209, and a next wafer is taken out from the wafer carrier 204 by the conveying means 208, and the wafer is conveyed to the sending-in load-lock chamber 203 having been replaced by an atmosphere ambience. Then, the operations at steps S205-S208 are repeated to wafers of a predetermined unit.
When plural load-lock chambers are used such as described above, the useless time in which no exposure process is carried out at the exposure station can be reduced. However, there is still a useless time at step S206.
Such useless time in which no exposure process is carried out at the station is attributable to the total time of the wafer conveyance time plus the load-lock chamber ambience replacement time being longer than the exposure process time. However, it is very difficult to shorten these time periods. For, the wafer conveyance time Ttr includes time for taking a wafer out of the wafer carrier, time for conveying the wafer out of the load-lock chamber and conveying it to the exposure station, as well as time for wafer rough alignment to be done during the conveyance. Taking the time necessary for such wafer transfer or wafer rough alignment into account, practically it is very difficult to shorten the wafer conveyance time Ttr by very much.
Also, as regards the time necessary for vacuum evacuation in the ambience replacement time Thxe2x86x92a or Taxe2x86x92h, it is determined by the gas discharging rate of an evacuation vacuum pump, the discharge-to-pressure characteristic of the pump, the volume of the load-lock chamber and the conductance of a pipe that communicates the load-lock chamber with the vacuum pump. There is a limit to making the load-lock chamber volume small, relative to the wafer size. Also, in order to shorten the evacuation time, the gas discharging rate of the pump must be made extraordinarily large. This is not practicable
Further, in order to shorten the wafer conveyance time, a wafer carrier may be provided in a load-lock chamber. However, it is contradictory to reduction of vacuum evacuation time and, practically, the throughput is slowed down.
As described above, in the wafer processing system and the wafer conveyance sequence, there are inconveniences to be solved to meet requirements of increases in the throughput.
It is an object of the present invention to provide a substrate processing system and/or a substrate conveying method wherein a plurality of load-lock chambers are used and wherein the total conveyance time is shortened thereby to increase the throughput.
In accordance with an aspect of the present invention, there is provided a substrate processing system, comprising: a process chamber having a process station for processing a substrate in an ambience different from an atmosphere; a plurality of load-lock chambers each being connected to said process clamber and to the atmosphere through an opening/closing device; first conveying means disposed in said process chamber, for conveying the substrate between said process chamber and said load-lock chambers; and second conveying means disposed in the atmosphere, for conveying the substrate between a supply station in the atmosphere and said load-lock chambers; wherein each of said load-lock chambers is arranged both for sending-in and sending-out of the substrate, and wherein, in each load-lock chamber, ambience replacement is carried out after the substrate is sent into or out of the load-lock chamber.
The process chamber may be provided with a stand-by station adjacent to said process station, for temporarily holding the substrate having been processed.
The first conveying means may convey the substrate between said process station, said load-lock chambers, and said stand-by station.
When there is no substrate at said process station, said first conveying means may convey it substrate from one of said load-lock chambers to said process station, and to convey a substrate, having been processed and being placed at said stand-by station, to one of said load-lock chambers from which the substrate has just been conveyed to said process station.
In accordance with another aspect of the present invention, there is provided a substrate conveying method in a substrate processing system including (i) a process chamber having a process station for processing a substrate in an ambience different from an atmosphere, (ii) a plurality of load-lock chambers each being connected to the process chamber and to the atmosphere through an opening/closing device, (iii) first conveying means disposed in the process chamber, for conveying the substrate between the process chamber and the load-lock chambers, and (iv) second conveying means disposed in the atmosphere, for conveying the substrate between a supply station in the atmosphere and the load-lock chambers, the substrate conveying method being for conveying a substrate between the supply station and the process chamber through the load-lock chambers, wherein plural substrates are sequentially supplied from the supply station to the load-lock chambers, and wherein, in each of the load-lock chambers, ambience replacement is carried out after both sending-in and sending-out of a substrate are performed.
The process chamber may be provided with a stand-by station adjacent to the process station, for temporarily holding the substrate having been processed.
The first conveying means may convey t)he substrate between the process station, the load-lock chambers, and the stand-by station, and, when there is no substrate at the process station, the first conveying means may convey a substrate from one of the load-lock chambers to the process station, and to convey a substrate, having been processed and being placed at the stand-by station, to one of the load-lock chambers from which the substrate has just been conveyed to the process station.